Hi,
Here is how to read this: fabric #5 (= the fifth most used fabric in the design) is used in 19 different patches/pieces. When using 43" wide fabric, a single strip of 2" should suffice to cut all those pieces from.
So maybe your design has 19 square patches of less than 2"x2", that would match the description.
Usage is estimated based on the size of the largest piece and the total area of fabric needed (including seam allowance).
Best regards,
Arnout